I. Technical Field
The present invention relates to a polishing apparatus and a substrate processing apparatus, and more particularly to a polishing apparatus for removing surface roughness produced at a peripheral portion (a bevel portion and an edge portion) of a substrate such as a semiconductor wafer, or for removing a film formed on a peripheral portion of a substrate, and to a substrate processing apparatus having such a polishing apparatus.
II. Description of the Related Art
In recent years, according to finer structures and higher integration of semiconductor devices, it has become more important to manage particles. One of the major problems in managing particles is dust caused by surface roughness produced at a bevel portion and an edge portion of a semiconductor wafer (substrate) in a fabrication process of semiconductor devices. In this case, a bevel portion means, as shown in FIG. 11, a portion B having a curvature in a cross-section of an edge of a semiconductor wafer W, and an edge portion means a flat portion E extending about several millimeters radially inwardly from the bevel portion B of the wafer. Hereinafter, the bevel portion and the edge portion will be collectively referred to as a peripheral portion.
In the fabrication process of the semiconductor devices, a large number of needle-like fine projections may be formed on the peripheral portion of the semiconductor wafer, thereby producing the surface roughness. The needle-like projections may be broken in transferring or processing the semiconductor wafer and thus produce the particles. Since such particles lead to a lower yield, it is necessary to remove the needle-like projections formed on the peripheral portion of the semiconductor wafer.
There has recently been a tendency to use Cu as interconnect material of the semiconductor devices and to use low-k material as dielectric. If Cu formed on the peripheral portion of the semiconductor wafer is attached to an arm of a transfer robot or a cassette in which the semiconductor wafer is accommodated, Cu may be diffused to contaminate other processes, resulting in a so-called cross contamination. Since low-k film has a very low strength, it may be detached from the peripheral portion of the semiconductor wafer during CMP process and may damage, e.g. scratch, a patterned surface. Therefore, it is important to completely remove Cu and low-k film from the peripheral portion of the semiconductor wafer.
From such situations, in the semiconductor fabrication process, the polishing of the peripheral portion of the substrate is carried out using a polishing tape having fixed abrasive attached on a surface thereof. In this kind of polishing process, the polishing tape is brought into sliding contact with the peripheral portion of the substrate while the substrate is being rotated, thereby removing the needle-like projections and the film formed on the peripheral portion of the substrate. However, when the polishing tape is in sliding contact with the peripheral portion of the substrate, polishing wastes (shavings) are scattered around the substrate. If such polishing wastes are attached to the device part of the substrate, defects may be caused in this device part, resulting in a low yield. Therefore, it is necessary to prevent the polishing wastes from attaching to the substrate. Further, also in a cleaning process, a drying process, and a substrate-transferring process after the polishing process, it is necessary to prevent the polishing wastes and particles, which have been produced in the polishing process, from attaching to the substrate.